Nitrogen Cycle
- - Nitrogen not used directly by living organisms - - Nitrogen gas constitute 78% of the air Nitrogen fixation This describes how nitrogen gas from the air is converted into nitrates. Plants use the nitrates as fertilizer. This occurs by two methods 1. Lightening : Lightening causes N2 gas to react with H2O molecules in the atmosphere and form ammonia and nitrates 2. Nitrogen fixing bacteria: some plants, especially leguminous plants, have bacteria living in their root nodules. These bacteria convert the atmospheric nitrogen to nitrates. E.g. of bacteria: Rhizobia Nitrification Animals and plants produce waste. Also, when they die, their body starts to decompose. Ammonia is released, which is then converted to nitrites. The Nitrifying bacteria, such as Nitrosomanas , convert the ammonia to nitrites, and the nitrites to nitrat...